The present invention relates to a wiper apparatus to be attached to a vehicle such as a truck, a bus, and an automobile, etc.
Generally, in this type of a wiper apparatus, there is one in which a wiper arm equipped with a blade at its tip end is constructed so as to reciprocatorily rock between upper and lower reversing positions on a window surface in order to wipe the window surface. Such a type of a wiper apparatus is devised so that a drive axis is integrally mounted at the base end portion of a wiper arm, and the wiper arm is caused to reciprocate and rock by rotating the corresponding drive axis clockwise and counterclockwise in interlock with drive of a wiper motor.
And, in this case, since it is requested that the wiping area of the blade based on reversing reciprocation of the wiper arm is made as wide as possible, the rotating range of the drive axis is determined with various conditions such as an area of a window, interference between the wiper arm and the blade attached to the tip end of the corresponding wiper, interference between the wipers adjacent thereto, etc., taken into consideration while meeting the abovementioned condition.
The wiper arm is devised so as to be able to change over from a high-speed motion to a low-speed wiping motion or vice verse to deal with the amount of precipitation. However, the wiping action of the wiper arm is constructed so as to rock on the basis of clockwise and counterclockwise rotation of the drive axis directly connected to the base end thereof. Therefore, in a case where wind pressure changes, the friction coefficient with the window surface changes, or the inertia force of the wiper arm is increased by changeover of the moving speed of the wiper arm to its high-speed side, the wiper arm may be subjected to overrun by which the wiper arm moves beyond the reversing position upon receiving of the abovementioned changes and large inertia force. In such a case, unless the overrun is taken into consideration as the moving range of the drive axis, the blade is brought into contact with a pillar and may overrun from the window surface. To prevent this, a problem occurs in that the wiping area needs to be reduced. This is an object of the invention.
The present invention was made in view of the situations described above and was developed to solve the abovementioned problem. It is therefore an object of the invention to provide a wiper apparatus equipped with a wiper arm reciprocating and reversing mechanism having a blade at its tip end and reciprocating and reversing between the upper and lower reversing positions using a pivotal axis, which is axially supported at the vehicle body side so as to rock, as a fulcrum point, wherein the wiper arm reciprocating and reversing mechanism the first link, one end of which is pivotally supported at the first pivotal axis provided so as to rock integral with the wiper arm, and the second link, one end of which is pivotally supported at the other end of the first link via the second pivotal axis and the second axis of which is pivotally supported at the vehicle body side via the third pivotal axis, and wherein reciprocating and reversing actions of the abovementioned wiper arm are carried out by a link motion of the second pivotal axis using the third pivotal axis as a fulcrum, and a rocking motion of the abovementioned wiper arm to the maximum extent of movement is carried out by a linked rocking in which the first, second and third pivotal axes are positioned in the same straight line.
And, by the abovementioned structure, while the overrun of the wiper arm is regulated, the wiping area can be established to a large extent.
In such a structure, the first pivotal axis of the invention may be provided at an intermediate portion of the wiper arm.
In such a structure, the first pivotal axis of the invention may be provided at an auxiliary link that turns around integral with the wiper arm.
Also, in such a structure, a wiper arm according to the invention is constructed so that the wiper arm is positioned at the maximum rocking end at the upper reversing position where the first, second and third pivotal axes are located in the same straight line in order, and is positioned at the minimum rocking end at the lower reversing position where the first, third and second pivotal axes are located at the lower reversing position in order.
Still further, in such a structure, a wiper arm according to the invention is constructed so that the maximum rocking position, where the first, second and third pivotal axes are located in the same straight line, is established as its upper reversing position, and the moving speed is decelerated when approaching the corresponding upper reversing position, whereby the inertia load may be reduced when the wiper arm is reversed at the upper reversing position, overrun can be eliminated, and an impact due to reversing can be reduced.